Planographic printing plate having mercurialized ink refusing areas for photomechanical printing



June 23, 1931. A. R. TRIST 1,811,734

PLANOGRAPHIC PRINTING PLATE HAVING MERCURIALIZED INK REFUSING AREAS FOR PHOTOMECHANICAL PRINTING Original Filed April 8, 1927 /lI/I/I/I/I. my

f a! 4994- fmad /37 Ji e/r7 4 Patented June 23, 1931 UNITED STATES PATENT OFFICE ARTHUR RONALD TRIST, OF LONDON, ENGLAND, ASSIGNOR TO WILLIAM .Y. DEAL OI MONTCLAIB, NEW JERSEY, AS TRUSTEE PLANOGRAPHIC PRINTING PLATE HAVING MERCURIALIZED INK REFUSING AREAS FOR PHOTOMECHANICAL PRINTING Application filed April 8, 1927, Serial No. 182,059, and in Great Britain May 18, 1926. Renewed October 28, 1930.

This invention relates to improvements in planographic printing plates having mercurialized ink refusing areas for photomechanical printing.

The invention has for one of its ob1ects a. printing plate capable of being produced more rapidly and with more faclllty, thereby rendering it particularly useful for newspaper printing and the like.

Another object of the invention is the production of such a plate at lower cost and by less skilled labour than has been possible heretofore.

A further object of the invention is the production of such a plate capable of effectmg more perfect impressions and at the hlghest printing speeds.

An additional object of the lnvent on 1s the production of a planographic printing plate of the type specified, which upon completion by unskilled labour, will be devold of protuberances or projectlng parts.

The invention has particular reference to planographic printing plates comprlsing a metal base plate, an under layer of metal to which mercury will adhere and an upper layer of metal to which mercury will not adhere, said upper layer of metal being etched away locally so as to form recesses which are filled with mercurial amalgam to produce a printing plate having printing areas and mercurialized non printing areas.

The invention consists in the formation of the recesses by dissolving away portions of the upper layer unprotected by resists by an etching fluid which chemically does not affect to any appreciable extentthe under layer of metal.

The invention is further characterized by 1 and modifications may be introduced in order to produce a printing plate adapted to suit amp particular printing requirements.

n the drawings:- Fig. 1 is a cross section through an improved plate constructed in accordance with this invention, the layers being diagrammatically illustrated in such a way as to clearly show the different layers;

Fig. 2 is a cross section of a similar plate showing local resists thereon, said local resists having been produced and deposited in any well known manner;

Fig. 3 illustrates such a plate after the differential etching has been effected:

Fig. 4 is a cross section through the improved plate after the resists produced by the etching process have been filled with a metallic deposit; and

Fig. 5 is a cross section through the improved plate in its finished state.

s the improved printing plate, about to be described, is to be used upon a printing machine having a magnetic bed, a base plate a of iron or mild steel is employed, said base plate a of iron receiving a coating of copper, c which in turn is coated with metallic chromium d.

It is essential that the finished plate shall not blister or be otherwise disintegrated by the steps in the formation of the printing surface, and to achieve that end it is essential that the copper layer 0 shall firmly adhere to the iron base a.

There are ways of producing a firmly adherent electrolytic layer of copper on iron or mild steel, well known to those skilled in the art of electroplating.

Experience has shown that the best results are obtained when the base plate a of iron to be electroplated is first immersed as an anode in a bath containing an approximately 10% solution of sulphuric acid and a current of high density, say about two hundred amperes per square foot is passed through it for two or three minutes. This anodic treatment so afii'ects the surface a of the iron or steel that metals electrolytically deposited thereon firmly adhere thereto at all parts.

After anodic treatment, the sheet of iron or steel is removed from the bath, washed and placed in a suitable bath for a short period of time to electrolytically deposit a thin layer I) of nickel thereon. This thin layer 6 of nickel ensures that the final coating 0 of copper shall have the greatest possible adhesion to the iron base a as it has been found that the adherence between copper and iron is materially increased if a thin layer of nickel is introduced.

After the flash coat I) of nickel has been deposited, copper is electrodeposited on the nickel surface from an ordinary sulphate of copper bath, the density of the current em ployed being suitably adjusted relative to the plating conditions so as to obtain a copper deposit having the requisite characteristics.

As soon as a layer 0 of copper of about three to ten one thousandths part of an inch in thickness has been deposited, the sheet is removed from the sulphate of copper bath, washed and introduced into a bath containing any standard chromium electrolyte, such, for example, as that described by Sargent.

A very thin layer (Z of chromium is deposited upon the copper'surface from this bath by means of a current of about one hundred and twenty-five amperes per square foot, and when the deposit d of chromium is from one to two ten thousandths part of an inch in thickness, after suitable washing, the prep aration of the plate is finished.

To form a printing surface on such a plate, any ordinary resist, for example, burnt-in enamel, may be locally applied in well known manner and in Fig. 2 the improved plate is shown with local resists c thereon. A light sensitive enamel is applied to the surface of the plate. The light sensitive surface is then exposed to the negative containing the image to be printed, preferably by means of a point source of light. The exposed surface is then developed in the well known manner to leave the chromium non-printing areas exposed, the enamel remaining on the surface of the plate in the printing areas.

The chromium layer (2 unprotected by enamel is now dissolved or etched away by immersing the plate in an etching medium which has a selective action on the chromium of the layer (2 relative to the copper of the under layer 0.

Hydrochloric acid solution has been found to be suitably selective, inasmuch as it will dissolve chromium much more readily than copper, indeed, so far as this invention is concerned, the copper may be said to be unaffected either by the hydrochloric acid solution or by the chemical compound formed during the etching of the upper layer. In view of this, the plate may be left in the acid solution sufiiciently long to completely remove the exposed chromium from the smallest areas without fear that any copper will be dissolved away from the larger areas, which are freed from the chromium more quickly. The solution of hydrochloric acid which has been found to give the best results is composed of one volume of pure concentrated hydrochloric ac d solution and three volumes of commercial glycerine.

When those parts of the chromium of the layer (Z unprotected by the resists c has all been dissolved away, the plate after being washed is treated with a solution of a salt of a metal, or salts of metals, with which mercury will amalgamate, such, for example, as cyanide of gold, cyanide of silver, or other salt of gold or silver, which will leave a firmly adherent deposit 7 of gold or silver on the exposed parts of the layer 0 cl copper. Obviously, if chemical action is relied upon for this deposition, it may be that the thickness of the layer 7' chemically deposited will be insufficient. to completely fill up the recesses in the layer (1. To overcome this, a current may be passed through the printing plate as a cathode whilst in the solution so as to increase the thickness of the layer 7 of metal, such as gold or silver, until it exactly fills up the recesses formed by the etching fluid, with the result that finally the upper surface of the metal deposit or deposits 7 is exactly level with the outer surface of the chromium layer d.

It is to be noted that when chromium forms the upper layer, no trouble is experienced with nodular formations about the edges of the recesses filled, owing to the absence of any deposit of metal upon the edge of the chromium by chemical or electrolytic treatment. Thus, it will be seen that it is possible to exactly fill up each recess to produce a pianographic printing surface.

After washing and drying, the plate is polished with mercury and chalk, resulting in the deposition of mercury on the gold or silver, thus forming an amalgam in the nonprinting areas which will refuse printers ink.

In the foregoing example an iron base with a copper under layer and a chromium printing layer has been referred to, but, obviously,

.LUil

lua'

metals other than iron, copper and chromium may be employed. For instance, if the finished printing plate is not required to have magnetic properties, then the iron plate may be substituted by a plate of other metal, similarly the chromium and copper may be replaced by other metals which can be differentially etched in the manner explained pro vided that the metal substituted for chromium is unaffected by mercury, whilst the metal substituted for copper will amalgamate with mercury.

1. An improved planographic printing plate comprising a metal base plate, an under layer of metal, an upper layer of metal which is unaffected by mercury and which is locally etched away to leave printing areas, said up- 1 iii per layer of metal being soluble in an ctching fluid which does not substantially dissolve the under layer of metal to which mercury will adhere, and mercurialized nonprinting areas, characterized by the use of an iron base plate having a firmly adherent electrolytically deposited under layer of copper thereon, said layer of copper having an electrolytically deposited upper layer of chromium adapted, after etching, to serve as a printing surface.

2. An improved planographic printing plate comprising an iron base plate, an under layer of copper, an upper layer of chromium ada ted, after etching, to serve as a printing surface, and mercurialized non-printing areas characterized by an electrolytically deposited layer of nickel being introduced between the iron base plate and the under layer of copper.

3. An improved planographic printing plate comprising a base plate of ferrous and magnetic material, having a surface thereof stripped by anodic action, a layer of nickel on said anodically stripped surface, an under layer of copper and an upper. layer of chromium, recesses in the layer of chromium, exposing the layer of copper thercthrough, and a filling of silver amalgamated with mercury in each of the recesses.

4. An improved planographic printing plate comprising ink retaining areas of chromium and ink refusing areas of mercurial amalgam supported on copper.

5. An improved planographic printing plate comprising ink retaining areas of chromium and ink refusing areas of mercurial amalgam supported on copper, said areas of chromium being electroplated on said copper and said areas of amalgam being held in recesses on said copper.

6. A process of producing printing plates having ink retaining areas formed of chromium and ink refusing areas formed of a mercurial amalgam supported by copper, characterized in, after the ap lication of local resists to the outer layer 0 chromium, the

exposed parts thereof being removed by an etching fluid, composed of hydrochloric acid solution and glycerine, to expose the copper which is then mercurialized.

7. A planographic printing plate comprising printing areas of chromium, and nonprlnting areas of mercurial amalgam.

8. A planographic printing plate comprising printing areas of chromium, recesses in said chromium areas, said recesses containing mercurial amalgam, and said mercurial amalgam forming the non-printing areas of said plate. 1

9. A planographic printing plate comprising printing areas of chromium and nonprinting areas of mercuryamalgamated with a precious metal.

10. A planographic printing plate comprising printing areas of chromium and nonprinting areas of mercury amalgamated with silver.

11. A planographic printing plate comprising printing areas of chromium, recesses in said chromium areas, said recesses containing mercury-silver amalgam, and said mercury silver amalgam forming the non-printing areas of said plate.

12. The method of producing a planographic printing plate having mercurial nonprinting areas which comprises electro-plating chromium upon a metallic base, app1y-,

ing a resist printing surface to the surface of said chromium, etching away said chromium in the non-printing areas of said plate, by exposure to an etching fluid containing hydrochloric acid and glycerine, and filling in the etched away portions of said plate with a mercurial amalgam.

13. The method of producing a planographic printing plate having mercurial nonprinting areas which comprises electro-plating chromium upon a metallic base, applying a resist printing surface to the surface of said chromium, etching away said chromium in the non-printing areas of said plate, by exposure to an etching fluid containing hydrochlori'c acid and glycerine, and filling in the etched away portions of said plate with a mercury-silver amalgam.

ARTHUR RONALD TRIST. 

